The advent of improved photocopy equipment, mainly high-resolution color photocopy equipment, has presented a real challenge to thwart the unauthorized duplication of original documents. The quality of the reproductions is often so good that, it may be difficult to distinguish original copies from color reproductions. Many methods, products and security features have been developed to prevent the unauthorized reproduction of original valuable documents, such as currency, travelers checks, checks, RX prescription pads, coupons, gift certificates, licenses, passports, personal identification papers, as well as packaging material for brand protection to deter illegal activities such as counterfeiting. Generally these methods, products and security features may be formed by a pattern of dots, lines, screen structures or the like. Within the background pattern, additional information may be printed that is mostly hidden by the background pattern when viewed by a casual observer. The additional information may typically include a security warning such as the word “VOID” or “COPY”. The security warning may become prominent on the copy such that even a casual observer will notice it. Thus, the original document may be easily distinguishable from its copied version by virtue of a warning such as “VOID” or “COPY” being prominently displayed on the copied version.
Many conventional approaches disclose various ways for providing methods and products that may enable copies of documents to be distinguished from the originals such as the use of a “large dot-small dot pattern” as described in such U.S. Pat. Nos. 4,227,720, 4,265,469, 4,310,180 and 4,341,404, the teachings of which are incorporated herein by reference, or a alternative version of the “large dot-small dot pattern” as to use bands of “large dot-small dot pattern” in varying dot sizes as described in such U.S. Pat. No. 5,340,159, the teachings of which are incorporated herein by reference, or “line screen pattern” as described in such U.S. Pat. Nos. 5,018,767, 5,193,853, 5,707,083, and 5,788,282, the teachings of which are incorporated herein by reference, in predetermined lines per inch spacing and line angles with the intention of producing distortion security screen. In such a manner, the latent images may be difficult to differentiate when being inspected with the unaided eye. However, hidden indicia may become apparent if the document is copied by color or black and white photocopiers. The principle method may include creating a disparity between the respective line screen values of the background pattern and the screen values of the hidden warning message that may allow the hidden warning message to appear on a reproduction of the original.
Also, many conventional approaches may incorporate a camouflaging pattern as described in U.S. Pat. No. 4,176,859, the teachings of which are incorporated herein by reference, to better disguise or suppress the visual appearance of the hidden warning message against its background pattern making it even more difficult to differentiate when being inspected with the unaided eye. However, the adverse effect of such a camouflaging pattern layer is that it may decrease the effectiveness of the security screen, masking or eliminating much of the security screen causing many geometric patterns not to be conducive for use to create and produce a highly distortion security images.
Other conventional approaches as described in U.S. Pat. No. 6,396,927, the teachings of which are incorporated herein by reference, may use a camouflaging layer, which may comprises a camouflage pattern that may be printed in thermochromic ink, which may vary with temperature. The camouflaging layer may be inactivate at room temperatures so that the latent message may be suppressed on the original document, and activated at scanning temperatures so that the latent message may be exhibited on a reproduction of the original document. The effectiveness of the thermochromic inks may be highly dependent of the condition and/or age of the documents, as well as the scanning temperatures of the copiers.
Therefore, what may be needed is a copy evident document protection method and apparatus that enables a simple and expedient way to incorporate improved distortion security images into a duo-tone, tri-tone and/or up to full multi-tonal printed documents, that may more effectively conceal the visual appearance of the hidden warning message on the original document using any camouflaging pattern without limitation or restriction, and at the same time, increase the effectiveness of the effect of the hidden message on a reproduction of the original document.
Moreover, what may be needed are methods for producing such duo-tone, tri-tone, and/or up to full multi-tonal original documents having such improved distortion security features calibrated, modified, transformed and/or customized for each printing process such as offset printing (lithography), letterpress, flexographic, intaglio and/or gravure techniques as well as for digital output equipment such as laser printers or printer/copiers and/or ink-jet printers and/or digital presses at any resolution.
Additionally, what may also be needed is a document protection method and apparatus that may enable a simple and expedient way to incorporate improved distortion duo-tone, tri-tone and/or up to full multi-tonal security features, that may vary from document to document, printed on demand, printed at any resolution, printed using laser printers (including laser copier/printer) and/or ink-jet printers and/or DI (direct image) presses and/or sheet/web, ink/toner based digital presses such as but not limited to presses from HP, Kodak, Xerox, Oce, Xeikon, etc., to prevent the unauthorized reproduction of original valuable documents through the use of photocopiers.